Types of dementias: the 8 forms of cognitive loss

Cognitive alterations due to brain deterioration have various manifestations.

Scientific advances in the field of medicine have allowed throughout history that we have gradually been able to overcome and survive a large number of diseases of different types, improving the quality of life and increasing our life expectancy.

However, there are still a large number of diseases and disorders that continue to pose a serious problem for our health and survival. Some of the major diseases to be tackled today are cancer, AIDS or the type of disorders to which this article is dedicated: the different types of dementias.

The concept of dementia

With the progressive increase in life expectancy and the drop in the birth rate typical of our society, the average age of the population is gradually increasing. Thus, little by little we are seeing an increasing increase in the aging of the population, with some of the disorders linked to or aggravated by age becoming more and more frequent. disorders linked to or aggravated by ageing are becoming more and more frequent.. Among them are dementias.

Dementia is a neurodegenerative disorder of organic origin characterized by a progressive loss of one or more mental faculties. loss of one or more mental faculties, which generally includes memory, along with other along with other abilities, which interfere with the proper functioning of the person's life and cause discomfort and / or loss of autonomy. The deficiencies detected represent a worsening with respect to previous performance and do not occur only in a situation of altered consciousness.

It is a question of a type of chronic, progressive and irreversible disorder (although in some cases the degenerative process may stop and there may even be a complete or partial recovery). (although in some cases the degenerative process may stop and there may even be a complete or partial recovery, as in those caused by hydrocephalus, intoxications or infections), produced by alterations in the organism linked to a disease, consumption of substances or deterioration and/or degeneration of the usual brain processes. In addition, its effects can vary according to the types of memory they affect more.

Classes according to the location of the lesions

In dementias, the nervous system is gradually impaired, deteriorating the different structures and nerve bundles and losing different functionalities over time as the disease progresses. However, the specific effects and deficits that each type of dementia will cause depend on the structures affected and the causes that lead to such degeneration.

Based on the location of the damage we can find several types of dementia.

1. Cortical dementias

Cortical dementias are those in which the main lesions are located at the level of the cerebral cortex. Due to the involvement of this part of the brain in information processing and deep work at the level of information processing, such involvement causes progressive loss of higher mental functions such as reasoning or abstraction, as well as the association between stimuli and concepts or memory.

In this type of dementia usually first appears an impairment of both anterograde and retrograde memory. (in the latter case temporally graded) followed by what is known as aphaso-apraxic-agnostic syndrome, in which problems appear in speech, sequencing of movements and recognition of stimuli.

Some of the best known cortical dementias are early Alzheimer's disease, frontotemporal dementias, Pick's disease or dementia with Lewy bodies.

2. Subcortical dementias

Subcortical dementias are those in which the subcortical structures, such as the basal ganglia, thalamus or brainstem, are particularly affected. Some of the most recognizable symptoms are those associated with a high level of motor slowing, the presence of motor slowing, the presence of passivity, lack of motivation, withdrawal, apathy, affective flattening, and alterations of the lobes of the brain. and alterations of the frontal lobes that cause the loss of executive functions.

While memory loss is also often present, in subcortical dementias it is just as severe regardless of when you are asked to remember, generally having a poor retrograde memory. Parkinson's dementia, HIV dementia and Huntington's chorea are some of the best known.

3. Axial dementias

This type of dementia mainly affects the limbic system, with its main symptoms being the deterioration of learning ability and working memory.. Although not usually considered a dementia, Korsakoff's syndrome is the best known case.

4. Global dementias

These are dementias in which there are features associated with lesions in both cortical and subcortical areas. Although in their origin the lesions may be localized in certain parts of the brain, in most dementias the degeneration of the nervous structures is associated with a degeneration of the brain. eventually affects the entire brain, such as Alzheimer's disease.such as Alzheimer's disease.

Main types of dementias

Regardless of their neuroanatomical location, some of the main types of dementias are as follows.

1. Alzheimer's disease

The best known and most common of the dementias, Alzheimer's disease, is a dementia of cortical origin (although it ends up being cortico-subcortical) of insidious origin. (although it ends up being cortico-subcortical) of insidious origin and slow progression that begins in the parieto-temporal area of the brain, with a progressive progression towards the frontal and the rest of the brain.

The cause of this disease is still unknown today, although in the brains of those who suffer from it, a high number of neurofibrillary tangles are observed. a high number of neurofibrillary tangles and beta-amyloid plaques..

There are usually three distinct phases. The first symptoms are usually impairment of recent memory, together with the presence of anterograde amnesia. A slight anomia and an impoverished language appears. Other alterations such as loss of olfactory capacity, loss of interest and motivation, rigid behavior and irritability also appear. Emotional distress and even depression are common at this stage, as there is often an awareness of illness. However, the patient is still able to be autonomous.

In a second phase, greater difficulties begin to appear, since it is at this time that the aphasia-apraxo-agnostic syndrome usually appears. Cognitive abilities deteriorate to a great extent, appearing retrograde amnesia and a high level of disorientation. In this state, the individual is no longer is no longer able to lead an autonomous life, requiring constant supervision..

In the last phase, the subject is no longer able to recognize neither significant people nor himself, losing language to the point of mutism and basic daily living skills. Over time he/she also loses motor skills, until he/she becomes permanently bedridden..

Frontotemporal dementias

Frontotemporal dementias are a subgroup of dementias also known as tauopathies (due to alterations in the tau protein) characterized by the fact that the main involvement occurs in the frontal and temporal lobes, resulting in great alterations of personality and in the area of the language..

There are three variants, frontal aphasia characterized by personality and behavioral changes, semantic dementia in which the loss of meaning of words stands out without changing other aspects of language, and primary progressive aphasia in which difficulties appear in all areas of language.

3. Dementia with Lewy Bodies

The most visible symptoms of this cortical dementia are severe attention and executive function problems, presenting aphaso-apraxo-agnostic syndrome, Parkinsonian type motor symptoms and hallucinations and delusions. Progressive onset and rapid course, intense psychotic symptoms and disorientation are very frequent.as well as sudden loss of consciousness.

Structures known as Lewy bodies usually appear in most of the cerebral cortex, together with a deficit of dopamine.

4. Due to prion disease or Creutzfeldt-Jakob disease

This is a dementia caused by the transmission of prions, proteins without nucleic acid that infect the nervous system. They cause sudden and rapid dementia, with motor problems such as tremors and spasms and abnormal functioning of neurons.

5. For Parkinson's disease

Parkinson's disease is a neurological disorder in which subcortical structures, especially the basal ganglia and substantia nigra (and especially the nigrostriatal pathway) progressively degenerate. A high prevalence of Lewy bodies can be observed in these areas.

This degeneration is caused by a deficit in the functioning of dopamine, the most characteristic symptoms being the appearance of parkinsonian tremors which occur especially in the resting state. There are also difficulties in walking, motor slowing, stooped posture, poor movements and facial expressionlessness.

Dementia associated with this disease, subcortical dementia, does not appear in all cases, although as the number of years since the onset of symptoms increases, it is more likely to appear. Typical symptoms of this dementia are the following slowing down both physically and mentally, together with a high level of passivity..

6. For Huntington's chorea

Huntington's chorea is a disorder of autosomal dominant genetic origin with complete penetrance that of complete penetrance that particularly virulently affects neurons governed by the neurotransmitter GABA and acetylcholine in the basal ganglia.

With a slow and progressive onset, in this neurodegenerative disease, constant uncontrolled movements appear in the form of twisting and turning of body parts reminiscent of a dance.

The dementia process, of a subcortical type, usually begins with behavioral and personality changes along with a marked alteration of the memory, with the appearance ofThe dementia process, of the subcortical type, usually begins with behavioral and personality changes along with marked memory impairment, with frontal lobe involvement eventually leading to a progressive loss of executive functions such as planning and sequencing.

7. Dementia due to HIV

HIV infection, after several years of evolution, can end up causing in some cases the degeneration of multiple brain structures and pathways, causing a particular type of dementia known as HIV-associated dementia complex.

This type of dementia, classified as subcortical, is characterized by the presence of slowing, reading problems, loss of spontaneity and hallucinations, decreased tracking movements and general movement impairment. It usually progresses rapidly to severe dementia, leading to the patient's death. leading to the patient's death.

8. Vascular or multi-infarct dementia

This type of dementia is caused by the presence of cerebrovascular accidents, either in the form of hemorrhage or stroke, affecting one or more parts of the brain. The effects can vary greatly depending on the area affected, producing a deterioration in some functions such as memory or language.

This is a type of dementia that, unlike most dementias, begins suddenly and abruptly, begins suddenly and abruptly, with the patient generally noticing the change in physical or mental status and abilities.. It is common for the deterioration to occur in a staggered manner, with some periods of partial recovery.

Bibliographical references:

• American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders. Fifth edition. DSM-V. Masson, Barcelona.

• Santos, J.L. ; García, L.I. ; Calderón, M.A. ; Sanz, L.J. ; de los Ríos, P. ; Izquierdo, S. ; Román, P. ; Hernangómez, L. ; Navas, E. ; Ladrón, A and Álvarez-Cienfuegos, L. (2012). Psicología Clínica. Manual CEDE de Preparación PIR, 02. CEDE. Madrid.